Center initial Gtk3 window by default to fix odd Rocky Linux 8 placement

Author: stackotter

Package.swift

@@ -71,6 +71,7 @@ let package = Package(
         .library(name: "DefaultBackend", type: libraryType, targets: ["DefaultBackend"]),
         .library(name: "UIKitBackend", type: libraryType, targets: ["UIKitBackend"]),
         .library(name: "Gtk", type: libraryType, targets: ["Gtk"]),
+        .library(name: "Gtk3", type: libraryType, targets: ["Gtk3"]),
         .executable(name: "GtkExample", targets: ["GtkExample"]),
         // .library(name: "CursesBackend", type: libraryType, targets: ["CursesBackend"]),
         // .library(name: "QtBackend", type: libraryType, targets: ["QtBackend"]),

Sources/Gtk3/Extensions/Widget+CastedPointer.swift

@@ -5,7 +5,7 @@
 import Foundation
 
 extension Widget {
-    func castedPointer<T>() -> UnsafeMutablePointer<T> {
+    public func castedPointer<T>() -> UnsafeMutablePointer<T> {
         return widgetPointer.cast()
     }
 }

Sources/Gtk3/Widgets/Window.swift

@@ -68,4 +68,8 @@ open class Window: Bin {
             gint(minimumSize.height)
         )
     }
+
+    public func setPosition(to position: WindowPosition) {
+        gtk_window_set_position(castedPointer(), position.toGtk())
+    }
 }

Sources/Gtk3Backend/Gtk3Backend.swift

@@ -94,6 +94,7 @@ public final class Gtk3Backend: AppBackend {
         if let precreatedWindow = precreatedWindow {
             self.precreatedWindow = nil
             window = precreatedWindow
+            window.setPosition(to: .center)
         } else {
             window = Gtk3.ApplicationWindow(application: gtkApp)
         }